Photographic silver halide supersensitized emulsions

ABSTRACT

A PHOTOGRAPHIC SILVER HALIDE SUPERSENTIZED EMULSION COMPRISING AT LEAST ONE SPECTRAL SENSITIZING DYE REPRESENTED BY THE FOLLOWING GENERAL FORMULA I AND AT LEAST ONE SPECTRAL SENSITIZING DYE REPRESENTED BY THE GENERAL FORMULA II:   Z1&lt;(-(4-(R1-OOC-)-1,2-PHENYLENE)-N(+)(-A-SO3(-))=C(-CH=   C(-C2H5)-C=C&lt;(-Z2-(4-W-1,2-PHENYLENE)-N(-B-SO3(-))-))-)   (X(-))N   WHEREIN Z1 AND Z2 EACH REPRESENT A MEMBER SELECTED FROM THE GROUP CONSISTING OF SULFUR AND A SELENIUM ATOM, R1 REPRESENTS A MEMBER SELECTED FROM THE GROUP CONSISTING OF A HYDROGEN ATOM, AND A LOWER ALKYL GROUP, W REPRESENTS A MEMBER SELECTED FROM THE GROUP CONSISTING OF A HYDROGEN, A HALOGEN ATOM, A LOWER ALKYL GROUP, AN ALKOXY GROUP, A HYDROXY GROUP, AND AN ARYL GROUP, A AND B EACH REPRESENT A MEMBER SELECTED FROM THE GROUP CONSISTING OF A POLYMETHYLENE AND AN ALKYL POLYMETHYLENE GROUP, AND M+ REPRESENTS A MEMBER SELECTED FROM THE GROUP CONSISTING OF A HYDROGEN CATION, A METAL CATION AND AN ORGANIC AMINE CATION,   Z3&lt;(-(1,2-PHENYLENE)-N(+)(-R2)=C(-CH=C(-C2H5)-CH=C&lt;(-Z4-   (1,2-PHENYLENE)-N(-R3)-))-)   WHEREIN Z3 AND Z4 EACH REPRESENT A MEMBER SELECTED FROM THE GROUP CONSISTING OF A SULFUR AND A SELENIUM ATOM, R2 AND R3 EACH REPRESENT A MEMBER SELECTED FROM THE GROUP CONSISTING OF A LOWER ALKYL AND SUBSTITUTED ALKYL GROUP, X- REPRESENTS AN ANION, AND N IS 0 OR 1, SAIDN BEING 0 WHEN THE DYE FORMS AN INTERNAL SALT.

United States Patent Office Patented July 3, 1973 45/ 28,168 U.S. Cl. 96124 7 Claims ABSTRACT OF THE DISCLOSURE A photographic silver halide supersensitized emulsion comprising at least one spectral sensitizing dye represented by the following general Formula I and at least one spectral sensitizing dye represented by the general Formula II:

wherein Z and Z each represent a member selected from the group consisting of sulfur and a selenium atom, R represents a member selected from the group consisting of a hydrogen atom, and a lower alkyl group, W represents a member selected from the group consisting of a hydrogen, a halogen atom, a lower alkyl group, an alkoxy group, a hydroxy group, and an aryl group, A and B each represent a member selected from the group consisting of a polymethylene and an alkyl polymethylene group, and M+ represents a member selected from the group consisting of a hydrogen cation, a metal cation and an organic amine cation,

wherein Z, and Z each represent a member selected from the group consisting of a sulfur and a selenium atom, R and R each represent a member selected from the group consisting of a lower alkyl and substituted alkyl group, X represents an anion, and n is or 1, said n being 0 when the dye forms an internal salt.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to photographic silver halide emulsions, and more particularly, to photographic silver halide emulsions supersensitized with a combination of two different types of spectral sensitizing dyes. To be more specific, this invention relates to a photographic silver halide emulsion having a high red-sensitivity and of which the wave length for the maximum sensitization lies between 625-665 nm.

(2) Description of the prior art In the art of making photographic halide emulsions, it is well known that, as the means of spectral sensitization of a silver halide emulsion through employment of a sensitizing dye, a certain kind of sensitizing dye is added to the silver halide emulsion. Moreover, the sensitizing wave length area of the resultant silver halide emulsion is extended to the longer wave length.

1 Nnno meter (minus 9 power of 1 meter).

Many of the photographic sensitive materials are required to be provided with various spectral sensitivity dependent upon the photographic purpose. For this, the desired spectral sensitivity is obtained usually by employing more than two sensitizing dyes at the same time.

However, such combined use of more than two sensitizing dyes often results in the sensitivity being lower than that attained when the sensitizing dye is used alone.

In a certain special case, however, the spectral sensitivity obtained through employing a certain sensitizing dye is superadditively strengthened when it is used in combination with a sensitizing dye or an organic compound having a certain limited structure. This phenomenon is widely known as supersensitization.

It is an important problem in the art of spectral sensitization to determine the suitable combination of the sensitizers to be employed which result in the desired supersensitization, and to obtain photographic sensitive materials having the desired spectral sensitivity.

SUMMARY OF THE INVENTION It is therefore, an object of the present invention to provide a photographic silver halide emulsion which is supersensitized to red light at 625-665 nm., by means of combining two different sensitizers.

The wave length of 625-665 nm. is widely used as a desirable spectral region for the black and white photographic sensitive material, or for the red sensitive layer of a color photographic material.

The object of the present invention has been achieved through the combined use of the spectral sensitizing dyes shown in the general Formulas I and II set forth below, in a photographic silver halide emulsion:

(I) 02m Z2 1 -CH=COH= R OOC W 1 Iii M4. III

wherein Z and Z each represent a sulfur atom or selenium atom; R represents a hydrogen atom, a lower alkyl group (e.g. methyl, ethyl, etc.) W represents a hydrogen atom, a lower alkyl group (e.g. methyl, ethyl, etc.) a halogen atom (e.g. chlorine, bromine etc.), an alkoxy group (e.g. methoxy, ethoxy, etc.), a hydroxy group, an aryl group (e.g. phenyl etc.), A and B each represent a polymethylene group (e.g. ethylene, trimethylene, tetramethylene etc.), an alkyl polymethylene group (e.g. methyl trimethylene etc.); and M+ represents a hydrogen cation, a metal cation (e.g. potassium, sodium etc.) or an organic amine cation (e.g. triethylammonium, pyridinium, S-benzylthiouronium, etc.),

wherein Z and Z each represent a sulfur atom or selenium atom, R and R each represent a lower alkyl group (e.g. methyl, ethyl, propyl, butyl, etc. preferably ethyl), a substituted alkyl group (e.g. sulto radical containing alkyl, such as y-sulfopropyl, -sulfobutyl, fi-sulfobutyl; a carboxy radical containing alkyl such as 'y-carboxypropyl; an alkyl group such as vinyl methyl etc.); X" represents an anion (e.g. halogen ion, perchlorate ion, thio cyanate ion, p-toluene sulfonate ion, bezene sulfonate ion, ethylsulfate ion, methyl sulfate ion etc.); and n is 0 or 1, said n being 0 when the dye forms aninternal salt.

As previously mentioned, the special feature of this invention resides in supersensitizing a photographic emulsion to the red spectral region by employing two kinds of cyanine dyestuffs as shown in the above general Formulas I and H; general Formula I being a cyanine dyestuff having a benzothiazole or benzoselenazole nucleus substituted with sulfo alkyl groups at the 3,3, positions and with COOH or COOOH at the 5 position, and the proper quantity of cyanine dyes represented by the general Formula II being used in combination with I. Further, it is possible to use together with the foregoing combination, a spectral sensitizer for increasing the sensitivity to the green spectral region (e.g. 2'-thiacyanine, 2,2'-cyanine, etc.).

DETAILED DESCRIPTION OF THE INVENTION The typical spectral sensitizers useful for this invention are shown below, but it should be understood that the invention is not to be limited thereto, since many modified structures of these spectral sensitizers may be made by one of ordinary skill in the art.

Dyes of IIContinued The sensitizers embraced by general Formulas I and II can be prepared by well known methods. For example, the dyes represented by general Formula I can be prepared according to the methods described in U.S. Pat. 2,503,776, German Pat. 1,072,765 and Japanese patent application 69-41466, while those of general Formula II can be prepared according to the methods described in U.S. Pat. 2,503,776, German Pat. 929,080 and Japanese patent application 68-65704.

Below is a method for the preparation of spectral sensitizer (IB) a typical example of Dye (I):

One gram of 5-methyl-3-(' -sulfopropyl)-2-thiopropio nylmethylenebenzothiazolien and 1.5 grs. of methyl ptoluenesulfonate were heated for 2 hours at C., then cooled and washed with ethyl ether. This reaction product was dissolved into 160 ml. of ethanol to which was added 1.4 grs. of anhydro-5-carbomethoxy-3-('y-sulfopropyl)-2- methylbenzothiazolium hydroxide and 2 ml. of triethylamine, and boiled for 3 hours under reflux. After removal of the solvent, the raw crystals were obtained by treating the residue first with ethyl ether then with a mixture of ethanol and acetone. 900 mg. pure crystals (M.P. C.) were obtained by recrystallization from a mixture of ethanol and isopropanol.

The other sensitizing dyes used in this invention can be prepared through a method analogous to that described above.

Some physical constants of the typical dyes to be used in this invention and represented by the general Formula I are mentioned in the table below. But it should be understood that the sensitizing dyes used in this invention are not limited thereto.

Ml. Dye No. C.)

A (MeOH) max. (nun) 1 Above.

The method of spectral sensitization described in this invention is effective for gelatino-silver halide emulsions, but it can also be effective for sensitizing emulsions containing hydrophilic colloids other than gelatin, such as collodion from agar, water-soluble cellulose derivatives, polyvinyl alcohol, and other hydrophilic synthetic or natural resins.

A mixed photographic silver halide emulsion, such as silver bromoiodide and chlorobromoiodide is preferably used in this invention.

The spectral sensitizers to be used in the present invention are dissolved in water or an organic solvent soluble in water (e.g. methanol, ethanol, acetone, methyl Cellosolve etc.), and added to the silver halide emulsion either separately or in a mixed state. The ratio of the spectral sensitizing dyes of the general Formula I to II to be contained in the emulsion may be varied in as wide a range as from 20:1 to 1:10 according to the effects desired. The photographic emulsion of the present invention may also be supersensitized or hypersensitized through the well known methods. Moreover, in preparing the photographic emulsion of the present invention various additives, such as chemical sensitizers, stabilizers, toners, hardeners, surface active agents, antifoggants, plasticizers, developing accelerator, color couplers and fluorescent whitening agents can be added to the emulsion by a common known method. The finished emulsion so obtained is coated onto a suitable support, such as. glass, a film base of cellulose derivatives or synthetic resin films, photographic baryta paper or paper-like synthetic or semisynthetic plastics.

A better understanding of the present invention will be obtained from the following examples, which are merely illustrative and not limitative of the present invention.

EXAMPLE 1 Three types of photographic silver halide emulsions were made by adding the spectral sensitizer to a silver bromide photographic emulsion (AgI:AgBr=7:93 mol):

(1) the sensitizer is one selected from general Formula I,

(2) the sensitizer is one selected from general Formula II,

and

(3) the sensitizer is a combination of (I) and (H).

Each photographic emulsion was coated onto a cellulose triacetate film base and dried to make a photographic sensitive material. The photographic sensitive materials thus obtained were exposed to light (64 lux, and corresponds to the color temperature 5400 K.) through a Fuji No. 7 filter (Fuji is a registered trademark made by Fuji Photo Film Co., Ltd.) which transmits only the light longer than 580 nm., and then developed with the developer having a composition as shown in Table 1.

TABLE 1 Gr. Methol 2 Sodium sulfite 100 Hydroquinone 5 Borax 2 Water up to 1 liter.

TABLE 2 Added quantity "i optical sensitizer Maximum (10" mol/kg. sensitivlt Red Dye No. emulsion) Emulsion (um. sensitivity 640 66 600 50 640 100 638 146 64.0 180 652 100 652 125 646 226 630 200 646 290 640 140 640 245 662 140 628 150 646 275 656 160 1 8.-.- AgBr/I 628 180 plus 1.... 6 plus 2.. AgBr 650 280 0 plus 6 plus 2 AgBr/I 650 255 D plus 5.-.- 8 plus 1 AgBr/I 662 195 In the Table 2, each value of the column red sensitivity shows the value compared to the red sensitivity of the photographic emulsion that is sensitized with the sensitizer E, and exposed to light through the Fuji Filter No. 7 (red filter). The sensitivity of the emulsion was assumed to be 100.

As is clearly shown in the Table 2, when the sensitizing dyes (I) and (II) are used in combination, the

red sensitivity is raised remarkably than when said sensitizing dyes (I) and (II) are used individually.

Although the present invention has been adequately described in the foregoing specification and examples included therein, one readily recognizes the fact that various changes and modifications can be made without departing from the spirit and scope thereof.

What is claimed is:

1. A photographic silver halide supersensitized emulsion comprising at least one spectral sensitizing dye represented by the following general Formula I and at least one spectral sensitizing dye represented by the general Formula 11:

wherein Z; and Z each represent a member selected from the group consisting of sulfur and a selenium atom, R represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group, A and B each represent a member selected from the group consisting of a polymethylene and an alkylpolymethylene group, and M+ represents a member selected from the group consisting of a hydrogen cation, a metal cation and an organic amine cation;

11 z, CH8 z,

0H=d-011= @Q .1) it it.

wherein Z, and Z each represent a member selected from the group consisting of a sulfur and a selenium atom, R and R each represent a member selected from the group consisting of a lower alkyl group, a sulfo radical containing alkyl group, a carboxy radical containing alkyl group, and an allyl group, X represents an anion, W is a member selected from the group consisting of a hydrogen atom, a halogen atom, a lower alkyl group, an alkoxy group, a hydroxy group, and an aryl group, and n is 0 or 1, said It being 0 when the dye forms an internal salt.

2. The photographic emulsion of claim 1, wherein with respect to the spectral sensitizing dye represented by the Formula I, each of Z and Z is a sulfur atom, R is a member selected from the group consisting of a hydrogen 7 containing alkyl group, and an allyl group.

4. The photographic emulsion of claim 1, wherein the sensitizing dye of Formula I is a member selected from the group consisting of (A) (CHzhSOa' (CH SOaHN(CgH) (CHzhSCa S HJ \N -OOH3 Ds a Wr sh and the sensitizing dye of Formula II is a member selected from the group consisting of zM Oa' H300 OC- 5. The photographic emulsion of claim 1 wherein the mole ratio of the spectral sensitizing dyes of the Formula I to II ranges from 20:1 to 1:10.

6. A photographic element comprising a support and the photographic silver halide emulsion of claim 1.

7. A photographic silver halide supersensitized emulsion comprising at least one spectral sensitizing dye represented by the following general Formula I and at least one spectral sensitizing dye represented by the general Formula II:

-so;- M+ B-SOr wherein Z and Z each represent a member selected from the group consisting of sulfur and a selenium atom, R represents a member selected from the group consisting of a hydrogen atom and a lower alkyl group, A and B each represent a member selected from the group consisting of a polymethylene and an alkylpolymethylene group, and M represents a member selected from the group consisting of a hydrogen cation, a metal cation and an organic amine cation;

wherein Z and Z each represent a member selected from the group consisting of a sulfur and a selenium atom, R and R each represent a member selected from the group consisting of a lower alkyl and substituted alkyl group whose substituents are members selected from the group consisting of a sulfo group and a carboxy group, X represents an anion, W is a member selected from the group consisting of a hydrogen atom, a halogen atom, a lower alkyl group, an alkoxy group, a hydroxy group, and an aryl group, and n is '0 or 1, said n being 0 when the dye forms an internal salt.

References Cited UNITED STATES PATENTS 2,647,050 7/1953 Firestine 96-137 2,647,051 7/1953 Vinton et al. 96-137 3,527,641 9/1970 Nakazawa et al 96-124 3,573,920 4/1971 Hiller 96-124 3,617,293 11/1971 Shiba et al. 96-124 J. TRAVIS BROWN, Primary Examiner U.S. Cl. X.R. 96-137 

